Kristin Bolinski
8/12/09
Human Physiology
Allometry Lab
Introduction: The definition of allometry is “growth of a part of an organism in relation to
the growth of the whole organism or some part of it.” Scientists use allometry to study the
relationship of body part sizes. It examines the relation between the size of an organism
and the size of any of its parts, or the size of body parts as they relate to each other. This lab
will compare height to arm span, the length of a foot to the length of a forearm, and the
length of a pinky finger to the length of a middle toe, in three people to illustrate how
allometry works.
Question: Which pair of human body parts is most proportional to each other, as
measured by the percentage difference of their lengths?
Hypothesis: Using the percentage difference of their lengths, I think that the foot and the
forearm are the most proportional body parts because I’ve noticed that when I hold shoes
in my hand they appear to be about the size of my forearm.
Materials: Transect tape, ruler, internet (google.com for conversions)
Procedure:
1. Measure the height on the dorsal side of the body, in inches, of one person using a
transect tape.
2. Measure the arm span (finger tip to finger tip) on the dorsal side of the body, in
inches for one person using the transect tape.
3. Record data in table.
Kristin Bolinski
8/12/09
Human Physiology
4. Repeat steps 1-3 for other two people.
5. Measure the length of the ventral side of the foot, in inches for one person, using the
transect tape.
6. Measure the length (proximal to distal) of the forearm (from the bump in the inside
of the elbow to the bump on the inside of the wrist), in inches for one person, using
the transect tape.
7. Record data in table.
8. Repeat steps 5-7 for other two people.
9. Measure the length (proximal to distal) of the left pinky finger, in inches for one
person, using the ruler.
10. Measure the length (proximal to distal) of the left middle toe, in inches for one
person, using the ruler.
11. Record data in table.
12. Repeat steps 9-11 for other two people.
13. Convert measurements from inches to centimeters using google.com. (Example:
Type [68 inches in centimeters] and it will give you {68 inches = 172.72
centimeters})
14. Find the percent difference of each measurement using this method:
a. Ex. – Height = 200cm, Arm span = 194cm
b. 194/200 = .97
c. .97 x 100% = 97%
d. 100% - 97% = 3% difference
Kristin Bolinski
8/12/09
Human Physiology
15. Find the average of each category’s percentages.
Prediction: If the foot and the forearm are the most proportional parts of the body, then
those two measurements will have the lowest percentage difference.
Data:
Eryn
Kristin
Mikaela
Height
Arm
Span
68 in
172.72
cm
62 in
157.48
cm
70 in
177.8
cm
67.5 in
171.45
cm
63 in
160.02
cm
69 in
175.26
cm
Percentage
Difference
.735%
1.587%
1.488%
Average =
1.27%
Analysis:
Foot
Forearm
9.5 in
24.13
cm
9.5 in
24.13
cm
10 in
25.4
cm
10 in
25.4 cm
9.5 in
24.13
cm
10.5 in
26.67
cm
Percentage
Difference
Pinky
Finger
Middle
Toe
Percentage
Difference
5%
2 in
5.08 cm
1 in
2.54 cm
50%
2.125 in
5.3975
cm
2.25 in
5.7150
cm
1.125 in
2.8575
cm
1.5 in
3.81 cm
0%
4.762%
Average =
3.254%
47.059%
33.3%
Average =
43.453%
Kristin Bolinski
8/12/09
Human Physiology
Conclusion: In conclusion, when trying to determine which pair of human body parts is
most proportional to each other, I thought that the foot and the forearm would be the most
proportional parts of the body. My hypothesis was proved false when comparing the
averages of each person, but was correct when looking at me individually. On average
between the three people measured for this experiment, the percentage difference between
height and arm span was the most proportional. Individually, my foot and forearm were
most proportional, Mikaela’s pinky finger and middle toe were most proportional, and
Eryn’s height and arm span were most proportional. There was one source of error found
with the transect tape that we used to measure ourselves with; it was off my one inch.